In recent years, WLEDs have demonstrated great potential to replace general lighting and illumination devices. A popular method of delivering white light in an LED is to combine a blue LED chip with yellow phosphor, but the technique can lead to colour disharmony and low light extraction between air and phosphor.

In the latest work, 300 nm ZrO2 nanoparticles and silicone binder were uniformly mixed together and then sprayed onto the surface of a phosphor layer by a pulsed method. When the CCT was measured at different emission angles, the angular-dependent deviations were seen to improve from 1000K to 420K over a range of –70 to 70 °C. This is due to the extra scattering capability provided by ZrO2 nanoparticles, which can be verified both by haze measurement and FDTD simulation. On the other hand, because the mixture of ZrO2 nanoparticles and silicone provides a refractive index gradient between air and phosphor layers, the light output was also observed to increase in this design.

A full description of the study can be found in the journal Nanotechnology.